The Association of Mine Surveyors of Zimbabwe AGM KARIBA 201 2

1. The Association of Mine Surveyors of Zimbabwe AGM KARIBA 2012 Technical Paper Title: Mine Ventilation Up-grade Management Presentation by : Joshua Tigere Group Occupational Hygienist

2. Presentation Overview • Definition of Mine Ventilation Up-grade • Implication of Mine Ventilation Up-grade • Need determination • Role Of the Mine Surveyor • Project justification • Proposed Projects appraisal • Practical example • Conclusion

3. Ventilation upgrade – definition This refers to a change in the overall Mine Ventilation capacity usually resulting in a higher pressure and intake volumes. This can be achieved through various ways some of which are: • Replacement of current main surface fans with bigger ones. • Installation of additional Main fans and intake shafts • Sinking of more intake airways to reduce overall mine resistance • Upgrade of the mine refrigeration capacity in the case of ultra – deep mines

4. Project Implications • Increased mine ventilation cost ( Purchasing of fans and ducting, Additional substation, Telemetry, increased electricity usage, security systems) • More airways in most cases presenting heat management challenges in ultra-deep mines. • Improved environmental conditions in the mine.

5. Determination of the need for a ventilation upgrade • The proposal should come from the initial Life of Mine Planning(LOMP) where the ventilation engineer spells out the stage by stage mine ventilation requirements in line with the development and production phases. • In other unusual cases, it may be necessitated by a desire to vary the initial production and development plan either due to unforeseen geological challenges or other initiatives

6. Role of the mine Surveyor • The mine surveyor assist in taking the survey from underground and site the proposed vent raise positions on surface • Assisting in siting of communication holes near the proposed raise bore sites • Measurement of distances to proposed sites to assist in budgeting for power lines and roads to sites • Alignment of machine on site prior to drilling

7. Project justification • A detailed write up should be generated spelling out the benefits of the up grade and reference must be made to the production and development needs that should be met. Issues to be considered include : • Overall mine Resistance and current Main fan duties • Current mine ventilation requirements • Projected mine ventilation requirements • State whether current system can/cannot meet the needs for the future • Present options for meeting the future ventilation requirements

8. Project Appraisals Appraise the available project proposals to refine decision making. Options that can be considered include the following: • Replacement of current main fans with bigger ones( in terms of fan duty) • Fan Selection and duct size selection • Raise-boring additional return shafts & Installation of additional main fans • Raise-boring additional intake airways

9. Ventilation Projects Appraisal • The Total Owning cost (TOC) Approach is used to determine the overall cost of owning a project over its life at today’s value. This includes the capital costs involved in the scheme and the present value of any running costs involved in the scheme. The technique is applied to all proposed projects and the method assists in determining the most economic project to implement.

10. An example of a comparison between two projects Challenge A volume of 45m3/s is being delivered to a section through a 3m x 3m tunnel which is 800m long. The pressure drop is 320Pa. It has become necessary to increase the quantity from 45m3/s to 65m3/s. The following schemes are being considered:

11. Scheme 1 Cost fan installation - $160 000 Fan Efficiency - 72% Motor Efficiency - 94% Power cost per kw per year - $1100 Life Expectancy of Section - 16yrs Present Value of $1 per year over 16yrs is $6.97 at 12%

12. Scheme 2 • Widening the airway from 3m to 4m, the pressure drop would again be 320pa when the new quantity flows. The cost of increasing the airway size will be approximately $300/m3. assume that none of the above changes will affect the operating point of the main fans

13. Question • Which is the most economical scheme?

14. Solution

15. Decision Making • From the above calculations, Scheme 1 is the most economical choice. In making deductions fro T.O.C calculations, the following needs to be taken into consideration prior to settling for an alternative;

16. Conclusion • A feasibility assessment of selected project given the available space, compatibility with existing infrastructure etc must be made prior to settling for an alternative. In other words the cheaper scheme is not always the best scheme. Practical considerations need to be made prior to making the final decision regards the best scheme to implement.

17. Role Of the Ventilation Engineer for Successful Vent upgrade project requirements • Competency in basic airflow and fan Engineering calculations • Knowledge of the cost of ventilation equipment to facilitate preparation of accurate budget for the upgrade project. • Knowledge of the cost of electricity in the country of operation • Mine ventilation planning knowledge • Must be conversant with the mine development and production budgets. • Must be conversant with present value tables and their application • Have ready contacts for companies that supply vent equipment and the Raise bore drilling companies

18. The End • Questions and comments